Analog video standards for broadcast television differ from country to country. The broadcast television standard used here in the United States, for example, is different than the broadcast standard used in France. Conventional standards include multiple versions of NTSC (National Television Standards Committee), multiple versions of PAL (Phase Alternate Line), and multiple versions of SECAM (Sequential Couleur Avec Memoire).
Broadcast frequencies also change from country to country. Each country is assigned a range of frequencies to allot to its domestic television broadcast service. An international governing body known as the “International Telecommunications Union” or “ITU” governs the allocation of broadcast frequencies among the various countries.
The country-by-country discrepancies among broadcast standards and channel frequencies pose a problem for television manufacturers. Since each country employs a particular standard and operates within a particular range of frequencies, manufacturers must tailor their televisions to the country into which they are to be sold. Traditionally, the manufacturers have hardwired the televisions during manufacturing to comply with the standard and frequency requirements of the destination country.
FIG. 1 shows the hardware components of a broadcast television, 20. It includes a tuner 22, a crossbar 24, a video decoder 26, a display 28, and speaker(s) 30. The tuner 22 tunes to a particular channel frequency to receive a broadcast television signal, which carries both video and audio data. The tuner 22 separates an analog video signal from an analog audio signal. The crossbar 24 routes the analog video signal to the video decoder 26, which converts the analog video signal to digital video data used to drive the display 28. The crossbar 24 also routes the analog audio signal to the speaker(s) or other audio components 30. It is noted that FIG. 1 represents a more modern television, which has digital capabilities. In older televisions, the crossbar 24 routes the analog video signal directly to the display 28 for depiction.
Under conventional manufacturing techniques, televisions used in different countries have different tuners 22 and video decoders 26. Televisions shipped in the United States are equipped with tuners and video decoders compatible with the U.S. broadcast standards and frequencies, whereas televisions shipped to other countries are equipped with different tuners and video decoders that are compatible with their broadcast standards and frequencies.
Country-based customization is inefficient because the manufacturer must make several versions of a product. In addition to broadcast standards and frequencies, the manufacturer might also have to contend with other regional differences, such specialized audio decoders for a particular market, or variations in picture tubes (e.g., 525 v. 625 line operation). The customization plays havoc with inventories because an overabundance of televisions for one country may not be cross-sold into another country where demand is strong.
To partially address this problem, manufacturers began using tuners and decoders that support multiple standards and frequencies. With this improvement, manufacturers are able to mass-produce one version of the television using the same components regardless of the destination country. Prior to shipping, the manufacturers program the tuner and decoder at the factory to a desired television standard and frequency range for the destination country.
While this is an improvement, it is not ideal. Video standards employed within a country may change. A country might decide to reallocate the broadcast frequencies, or perhaps adopt a different television standard, for political, administrative, or technical reasons. Televisions programmed at the factory are not capable of accommodating these changes. Accordingly, there is a need to design a television tuning system that may be upgraded in the field.
Another problem concerns portability. In the past, televisions sold into one country would typically reside in that country for the life of the product. It was less common for people to transport their televisions to different countries, unless they were permanently moving.
Today, as television tuner hardware decreases in size and continues to fall in component cost, it can be incorporated into portable computing devices, such as laptop computers. Given the portable nature of these computing devices, it is very likely that they will be used in numerous different locations throughout the world that employ different television standards and channel frequencies. Thus, there is a need for a worldwide television tuning system that is reconfigurable in the field to adapt to different television standards and channel frequencies.